Our research examines the linguistic, cognitive, and environmental conditions that give rise to natural language, in individuals and at the community level. The primary objective is to understand the abilities all human learners apply to language acquisition, and how those abilities change with age. The project centers on a generation of deaf Nicaraguan children and adults whose initial language environment included no previously developed sign language. When their community first formed in the late 1970s, this first generation began to create a new sign language, and in doing so acquired something more than what was available in their language environment. Nicaraguan Sign Language (NSL) continues to develop and change as new cohorts of children enter the community and learn the language from older peers. By using targeted elicitation and communication tasks to systematically compare each cohort to the one that preceded it, the proposed research program will investigate developments in areas central to the grammar of this emerging language, particularly the individual grammatical elements (e.g., words and morphemes), and the conventions for combining them into complex constructions (including word order and spatial devices). Together these comparisons will help reveal how human learners create, organize, and systematize language information, and how these abilities vary with age. PUBLIC HEALTH RELEVANCE This research addresses a question central to the issue of optimal learning environments for children. That is, in which areas is a rich environment crucial for full language development, and in which areas are children and able to make up for environmental gaps? The results will inform both researchers and clinicians about the complex interplay between natural human language abilities, the language environment, and language learning outcomes.